Three-Corner Hat Analysis of the Stability of UTC and Various UTC(k)s
Thomas E. Parker
The stabilities of some local UTC time scales have recently improved dramatically with the increasing use of cesium or rubidium fountains as nearly always present frequency references. Along with time scales using maser ensembles, there are now a number of very stable scales with comparable frequency stability. Improved frequency stability means better performance at serving as a local real time representation of UTC. It is now possible to perform a meaningful three-corner hat Allan deviation analysis to determine the individual stabilities of the best local UTC(k)'s, as well as UTC itself. Included in this analysis using data from Circular T are the local time scales at the US Naval Observatory, UTC(USNO), the National Institute of Standards and Technology, UTC( NIST), the Paris Observatory, UTC(OP), and in Germany, UTC(PTB). All local UTC(k)'s are of course steered to UTC, which artificially improves the apparent long-term stability (hundreds of days). Therefore, in addition to the UTC(k) time scales, the stabilities of two local free running atomic time scales, TA(k)'s, have also been analyzed along with TAI. Results of these evaluations are presented. Fractional frequency stabilities are in the range of 2x10-15 to 3x10-16 over various values of tau. The improved long-term stability achieved with nearly continuously operating fountains is clearly evident.
Proceedings of 2013 Precise Time and Time Interval (PTTI) Meeting
December 2-5, 2013
2013 Precise Time and Time Interval (PTTI) Meeting